JP2008181774A - Cylindrical non-sintering type alkaline storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylindrical non-sintering type alkaline storage battery suitable for having high capacity, with high productivity and quality. <P>SOLUTION: The cylindrical alkaline storage battery is provided with a cylindrical outer package can with conductivity, and an electrode group stored in the outer package can with alkaline electrolyte solution and made with a band-shape cathode plate and anode plate spirally wound through a separator. The cathode plate contains a three-dimensional mesh metal body made of a plurality of cylindrical branched parts and bar parts crossing the branched parts mutually, and an active material filled in the metal body. Mass par unit area of the metal body is 200g/m<SP>2</SP>or more. When a wall thickness of the branched part at a center part in a thickness direction of the metal body is Di, and a wall thickness of the branched part 42a near both surfaces of the metal body is Do, Do is smaller than Di and not more than 15 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cylindrical non-sintered alkaline storage battery.

  Examples of the alkaline storage battery include a nickel cadmium secondary battery and a nickel hydride secondary battery, depending on the type of active material contained, and these alkaline storage batteries include a cylindrical battery with a cylindrical outer can. is there. The outer can is sealed with a lid with a safety valve, and an electrode group is accommodated together with an alkaline electrolyte in the inside. The electrode group is formed by winding a strip-shaped negative electrode plate and a positive electrode plate in a spiral shape with a separator in between.

The positive electrode plate has a non-sintered nickel electrode, and the nickel electrode is formed by filling a positive electrode mixture in a nickel metal body having a three-dimensional network structure. The positive electrode mixture includes nickel hydroxide particles that are positive electrode active materials, additive particles, and a binder that binds these particles.
This type of cylindrical non-sintered alkaline storage battery is widely used as a power source for electronic and electrical devices such as digital still cameras. Since battery capacity affects the drive time of these devices, there is a strong demand for increased battery capacity and higher performance.

In order to increase the battery capacity, the positive electrode capacity that determines the battery capacity may be increased. In other words, the positive electrode active material contributing to the charge / discharge reaction may be increased. For that purpose, the volume (length, width, thickness) of the positive electrode plate and the packing density of the positive electrode mixture into the metal body may be increased. For example, Patent Document 1 discloses that the thickness is increased to 0.8 mm or more to increase the capacity. A nickel electrode that achieves the above is disclosed.
Japanese Patent Laid-Open No. 10-199520 (for example, claims)

The increase in the positive electrode active material may be accompanied by an increase in the density and thickness of the positive electrode plate. Particularly in the case of a cylindrical non-sintered alkaline storage battery, the increase in the density and thickness of the positive electrode plate The productivity and quality deterioration when winding a plate through a separator are caused. That is, the short-circuit failure due to the metal body constituting the positive electrode plate is increased.
The present invention has been made based on the above-described circumstances, and an object of the present invention is to provide a cylindrical non-sintered alkaline storage battery that is suitable for high capacity and has high manufacturability and quality.

In order to achieve the above-described object, according to the present invention, a cylindrical outer can having conductivity, and the outer can are accommodated together with an alkaline electrolyte, and a strip-like positive electrode plate and a negative electrode plate are respectively interposed via a separator. In a cylindrical non-sintered alkaline storage battery including a spirally wound electrode group, the positive electrode plate has a three-dimensional network composed of a plurality of cylindrical branch portions and nodes where the branch portions intersect with each other. A metal body and an active material filled in the metal body, wherein the mass of the metal body per unit area is 200 g / m ² or more, and the branch portion at the center in the thickness direction of the metal body Di is the wall thickness of the metal body, and Do is the wall thickness of the branch in the vicinity of both surfaces of the metal body. Do is smaller than Di and 15 μm or less. An alkaline storage battery is provided (claim 1).

In the cylindrical non-sintered alkaline storage battery according to claim 1 of the present invention, the short circuit failure is prevented by the wall thickness Do being smaller than the wall thickness Di and less than 15 μm. That is, since the wall thicknesses Do of the branch portions in the vicinity of both surfaces of the metal body are small, the branch portions are prevented from breaking through the separator and coming into contact with the negative electrode plate.
On the other hand, in this cylindrical non-sintered alkaline battery, since the mass per unit area of the metal body is 200 g / m ² or more, the utilization factor of the active material in the positive electrode plate even if the wall thickness Do is 15 μm or less. In addition, high discharge efficiency is ensured.

  As a result, according to the cylindrical non-sintered alkaline storage battery, high capacity can be realized while suppressing short circuit failure.

  FIG. 1 shows an AA size cylindrical non-sintered nickel-hydrogen secondary battery as a cylindrical non-sintered alkaline storage battery according to an embodiment of the present invention. The battery includes an outer can 10 having a bottomed cylindrical shape with one end opened, and the outer can 10 has conductivity and functions as a negative electrode terminal. In the opening of the outer can 10, a conductive cover plate 14 is arranged via a ring-shaped insulating packing 12, and the insulating packing 12 and the cover plate 14 are fixed in the opening by caulking the opening edge. Yes.

  The lid plate 14 has a gas vent hole 16 in the center, and a rubber valve element 18 is disposed on the outer surface of the lid plate 14 so as to close the gas vent hole 16. Further, a cylindrical positive terminal 20 with a flange covering the valve body 18 is fixed on the outer surface of the cover plate 14, and the positive terminal 20 presses the valve body 18 against the cover plate 14. Therefore, the outer can 10 is normally airtightly closed by the lid plate 14 together with the insulating packing 12 and the valve body 18. On the other hand, when gas is generated in the outer can 10 and its internal pressure increases, the valve body 18 is compressed, and gas is released from the outer can 10 through the gas vent hole 16. That is, the cover plate 14, the valve body 18, and the positive electrode terminal 20 form a safety valve.

  A substantially cylindrical electrode group 22 is accommodated in the outer can 10 together with an alkaline electrolyte (not shown), and the outermost peripheral portion of the electrode group 22 is in direct contact with the peripheral wall of the outer can 10. The electrode group 22 includes a positive electrode plate 24, a negative electrode plate 26, and a separator 28. Examples of the alkaline electrolyte include a sodium hydroxide aqueous solution, a lithium hydroxide aqueous solution, and a potassium hydroxide aqueous solution, and a mixture of two or more thereof. The aqueous solution etc. which were made can be used.

  Further, in the outer can 10, a positive electrode lead 30 is disposed between one end of the electrode group 22 and the lid plate 14, and both ends of the positive electrode lead 30 are connected to the positive electrode plate 24 and the lid plate 14. Therefore, the positive electrode terminal 20 and the positive electrode plate 24 are electrically connected via the positive electrode lead 30 and the lid plate 14. A circular insulating member 32 is disposed between the cover plate 14 and the electrode group 22, and the positive electrode lead 30 extends through a slit provided in the insulating member 32. A circular insulating member 34 is also arranged between the electrode group 22 and the bottom of the outer can 10.

  Referring to FIG. 2, in the electrode group 22, the positive electrode plate 24 and the negative electrode plate 26 are alternately overlapped when viewed in the radial direction of the electrode group 22 with the separator 28 interposed therebetween. This is because the electrode group 22 is provided with a strip-like positive electrode plate 24, a negative electrode plate 26, and a separator 28, respectively, and the positive electrode plate 24 and the negative electrode plate 26 are connected to each other by using a core from one end side of the separator 28. This is because it is formed in a spiral shape.

The outermost peripheral portion of the electrode group 22 is formed by a part on the winding end side of the negative electrode plate 26, and a part on the winding end side of the negative electrode plate 26 is in contact with the outer can 10. Accordingly, the negative electrode plate 26 and the outer can 10 are electrically connected to each other at the outermost peripheral portion of the electrode group 22.
As a material for the separator 28, for example, a polyamide fiber nonwoven fabric or a polyolefin fiber nonwoven fabric such as polyethylene or polypropylene provided with a hydrophilic functional group can be used.

  The negative electrode plate 26 has a conductive negative electrode core having a strip shape, and a negative electrode mixture is held in the negative electrode core. The negative electrode core is made of a sheet-like metal material having a plurality of through-holes. As such, for example, a punching metal, a metal powder sintered body substrate, an expanded metal, a nickel net, or the like can be used. . In particular, a punching metal or a metal powder sintered body substrate that is sintered after molding metal powder is suitable for the negative electrode core.

Since the battery is a nickel-hydrogen secondary battery, the negative electrode mixture is composed of hydrogen storage alloy particles and a binder capable of storing and releasing hydrogen as a negative electrode active material, but instead of the hydrogen storage alloy, for example, cadmium The battery may be a nickel cadmium secondary battery using the compound, and is not particularly limited. However, a nickel-hydrogen secondary battery is suitable for increasing the capacity of the battery.
The hydrogen storage alloy particles are not particularly limited as long as they can store hydrogen generated electrochemically in an alkaline electrolyte during battery charging and can easily release the stored hydrogen during discharge. Such a hydrogen storage alloy is not particularly limited, and for example, an AB ₅ type alloy such as LaNi ₅ or MmNi ₅ (Mm is a misch metal) can be used. As the binder, a hydrophilic or hydrophobic polymer can be used.

The positive electrode plate 24 is a non-sintered nickel electrode, and includes a conductive positive electrode core and a positive electrode mixture held on the positive electrode core.
The positive electrode mixture includes positive electrode active material particles, various additive particles for improving the characteristics of the positive electrode plate, and a binder for binding the mixed particles of these positive electrode active material particles and additive particles to the positive electrode core. It consists of an adhesive.

The positive electrode active material particles are nickel hydroxide particles because the battery is a nickel metal hydride secondary battery. However, the nickel hydroxide particles may be dissolved in cobalt, zinc, cadmium, or the like, or the surface is a cobalt compound. May be coated.
In addition, although there is no particular limitation, additives include, in addition to yttrium oxide, cobalt compounds such as cobalt oxide, metal cobalt, and cobalt hydroxide, zinc such as metal zinc, zinc oxide, and zinc hydroxide. Compounds, rare earth compounds such as erbium oxide, and the like, and hydrophilic or hydrophobic polymers can be used as the binder.

As schematically shown in FIG. 3, the positive electrode core is a nickel-like metal band 35 made of nickel, and has a mass per unit area (weight per unit area) of 200 g / m ² or more. Each metal body 35 has a three-dimensional network structure, that is, a porous structure, and has innumerable pores communicating with each other. In the positive electrode plate 24, the positive electrode mixture is held in a state of being filled in these pores.
In FIGS. 1 and 2, the metal body 35 and the positive electrode mixture are not distinguished from each other in order to avoid complication of lines.

The metal body 35 has a three-layer structure. Specifically, as shown by the one-dot chain line in FIG. 3, the metal layer 35 is positioned on the radially inner side of the electrode group 22 and positioned on the radially outer side. An outer layer 38, and a central layer 40 located between the inner layer 36 and the outer layer 38.
Although the configuration of the metal body 35 is substantially the same between the inner layer 36 and the outer layer 38, although there are some differences depending on the curvature of the positive electrode plate 24, the outer layer 38 and the central layer 40 will be described below.

As shown in an enlarged view in FIG. 4, the outer layer 38 of the metal body 35 includes innumerable branch portions 42a and nodes where the branch portions 42a intersect with each other, and the branch portions 42a and the nodes are innumerable. A pore is formed.
On the other hand, the central layer 40 of the metal body 35 also includes an infinite number of branch portions 42b and nodes where the branch portions 42b intersect each other, as shown in an enlarged view in FIG. Form countless pores.

However, the size of each pore in the central layer 40 is larger than that of the outer layer 38. In other words, the number of pores per unit volume (PPI: Pore per Inch) in the central layer 40 is larger than that of the outer layer 38. Smaller than that. For this reason, the surface area of the metal body 35 in the central layer 40 is smaller than that of the outer layer 38.
5 and 6 show cross sections of the branch portions 42a and 42b, respectively. Each of the branch portions 42a and 42b has a hollow cylindrical shape, but the wall thickness Do of the branch portion 42a of the outer layer 38 is thinner than the wall thickness Di of the branch portion 42b of the central layer 40 and is 15 μm or less. Therefore, the wall thickness of the branch portion of the inner layer 36 is also thinner than the wall thickness Di of the branch portion 42b of the central layer 40, and is 15 μm or less.

Since the battery described above can be manufactured by applying a normal method except for the positive electrode plate 24, an example of a method for manufacturing the positive electrode plate 24 will be described below.
First, three foamed urethane sheets are prepared in order to produce a positive electrode core. One of the prepared urethane foam sheets is subjected to a conductive treatment, and thereafter Ni plating is performed by an electrolytic plating treatment. Then, the remaining two urethane foam sheets are bonded to both surfaces of the Ni-plated urethane foam sheet to form a laminate. Note that the PPI of the two sheets that are pasted together is larger than that of the foamed urethane sheet plated with Ni previously.

  Thereafter, the laminate is subjected to conductive treatment, and further subjected to Ni plating by electrolytic plating treatment. As a result, the two urethane foams bonded together are also plated with Ni. Thus, the Ni-plated laminate is roasted to burn the urethane component and then heat-treated in a hydrogen atmosphere to obtain a metal body 35 having a three-layer structure. That is, the wall thicknesses Do and Di of the branch portions 42a and 42b correspond to the plating thickness of Ni plating.

As the conductive treatment, application of a conductive agent, chemical plating (electroless plating), or physical plating (Ni sputtering) can be used. The basis weight of the metal body 35 can be controlled by adjusting the Ni plating amount.
Next, the prepared metal body 35 is filled with a positive electrode mixture paste and dried. Then, the metal body 35 filled with the positive electrode mixture in a dry state is rolled to adjust the thickness, and then cut into a predetermined dimension, whereby the positive electrode plate 24 is obtained.

In the battery having the above-described configuration, the wall thickness Do of the branch portion 42a of the inner layer 36 and the outer layer 38 is smaller than the wall thickness Di of the branch portion 42b of the central layer 40 and is 15 μm or less, thereby preventing a short circuit failure. That is, since the wall thickness Do of the branch part 42a in the vicinity of both surfaces of the metal body 35 is small, the branch part 42a broken at the time of winding is prevented from breaking through the separator 28 and contacting the negative electrode plate 26.
On the other hand, in this cylindrical non-sintered alkaline battery, since the mass per unit area of the metal body 35 is 200 g / m ² or more, the active material in the positive electrode plate 24 can be obtained even when the wall thickness Do is 15 μm or less. Utilization rate and high rate discharge are ensured.

As a result, according to this battery, high capacity can be realized while suppressing the short-circuit failure rate.
The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in one embodiment, a foamed urethane sheet is used in the production of the metal body 35, but a material having a three-dimensional network structure such as a non-woven fabric can also be used. Also, a single urethane foam 35 and a nonwoven fabric may be combined to produce a single metal body 35.For example, a foamed urethane sheet is used for the production of the central layer 40, and a nonwoven fabric is used for the production of the inner layer 36 and the outer layer 38. It may be used.

  In one embodiment, in producing the metal body 35, the urethane foam sheet used to form the central layer 40 has a smaller PPI (pore diameter) than the urethane foam sheet used to form the inner layer 36 and the outer layer 38. The difference in surface area was used to make a large difference in wall thicknesses Do and Di, but three foamed urethane sheets with the same PPI were also used. Good.

Alternatively, two foamed urethane sheets having a relatively large PPI may be bonded to both surfaces of one foamed urethane sheet, and these sheets may be subjected to conductive treatment at the same time, followed by electroless plating. . In this case as well, the wall thicknesses Do and Di can be made different by utilizing the difference in surface area between the sheets and the difference in pore diameter.
In one embodiment, the metal body 35 has a three-layer structure, but may have a laminated structure of three or more layers, or the wall thickness Do may be different between the inner layer 36 and the outer layer 38. Good. That is, the wall thickness Do of the branch part 42a of each region from the inner peripheral surface and the outer peripheral surface of the metal body 35 to a depth of about 1/3 of the thickness of the metal body 35 is the thickness direction sandwiched between these regions What is necessary is just to be smaller than the wall thickness Di of the branch part 42b in a center part, and 15 micrometers or less. However, considering the productivity and cost of the metal body 35, the metal body 35 preferably has a three-layer structure.

  Further, in one embodiment, the core material such as urethane for producing the metal body 35 is eliminated by roasting, but the core material may remain without being roasted, and the branch portion 42a may be solid. .

1. Production of Battery of Example 1 (1) Production of Positive Electrode Plate First, a metal body as a positive electrode core was produced as follows.
Three urethane foam sheets each having a thickness of about 0.5 mm were prepared. Of these, two sheets have the same PPI and are larger than the other one. Then, a conductive sheet and an electrolytic plating process (first time) were sequentially performed on a single sheet having a small PPI, thereby forming a Ni plating having a mass per unit area of 150 g / m ² .

Then, two sheets having a large PPI were laminated on both sides of the Ni-plated sheet to form a laminate. The laminate was sequentially subjected to conductive treatment and electrolytic plating treatment (second time). In this second electrolytic plating treatment, Ni of 150 g / m ² is formed in mass per unit area, and 300 g / m ^{2 in} mass per unit area is formed by the first and second electrolytic plating treatments. Ni plating was formed.

After that, the laminated body that has undergone two electrolytic plating treatments is roasted to burn and remove the urethane component, and then heat-treated in a hydrogen atmosphere, and a metal body having a wall thickness shown in Table 1 having a wall thickness of 1.5 mm. Was made.
Next, the obtained metal body was filled with a paste to be a positive electrode mixture, and the paste was dried. Thus, the metal body filled with the positive electrode mixture was rolled so as to have a thickness of 0.9 mm, and then cut into a predetermined dimension to produce a positive electrode plate.

The paste was prepared by adding 40 parts by mass of a 0.2% by mass hydroxypropylcellulose aqueous solution and 1 part by mass of a 60% by mass PTFE dispersion to 100 parts by mass of the active material powder. The active material powder contains, as main components, particles having a highly conductive coating layer formed on the surface of nickel hydroxide particles and a cobalt compound. The coating layer is made of a higher cobalt compound containing sodium.
(2) Production of negative electrode plate A commercially available metal element was weighed and mixed so as to be Mm _1.0 Ni _3.4 Co _0.8 Al _0.2 Mn _0.6 and dissolved in a high frequency melting furnace. The molten metal was poured into a mold to prepare a hydrogen storage alloy ingot. The ingot was coarsely pulverized in advance, and then mechanically pulverized in an inert gas atmosphere until the average particle size became about 50 μm.

Next, a polyethylene oxide or the like as a binder and an appropriate amount of water are added to and mixed with the obtained hydrogen storage alloy powder to prepare a slurry that becomes a negative electrode mixture, and this slurry is a negative electrode made of a punching metal. It was applied to both sides of the core and dried. Then, the punched metal in which the dried negative electrode mixture was held on both sides was rolled to a predetermined thickness, and then cut into a predetermined dimension to prepare a negative electrode plate.
(3) Assembling the battery The obtained positive electrode plate and negative electrode plate were spirally wound as a separator through a polypropylene non-woven fabric having a thickness of 0.15 mm to produce an electrode group, and this electrode group was placed on an AA size outer can. Inserted. Then, while attaching the positive electrode lead to the cover plate, 7.0N alkaline electrolyte was poured into the outer can. This alkaline electrolyte contains 1.0N LiOH, 1.0N NaOH, and 5.0N KOH. Then, the lid edge was fixed by crimping the opening edge of the outer can, and 100 AA-sized cylindrical non-sintered nickel-hydrogen secondary batteries were produced.

2. Production of Battery of Comparative Example 1 100 batteries of Comparative Example 1 were produced in the same manner as in Example 1 except that a metal body as a positive electrode core was produced as follows.
First, a urethane foam sheet having a thickness of about 1.5 mm was prepared. The PPI of this sheet is the same as the smaller PPI used to form the center layer of the two types of PPI used in Example 1. This sheet was sequentially subjected to a conductive treatment and an electrolytic plating treatment to form a Ni plating having a mass per unit area of 300 g / m ² .
Thereafter, the electrolytically plated sheet was roasted to burn and remove the urethane component, and then heat-treated in a hydrogen atmosphere to produce a metal body having a wall thickness shown in Table 1 and having a wall thickness of 1.5 mm.

3. Battery Evaluation (1) Wall Thickness of Branches In the positive electrode plate manufacturing process of Example 1 and Comparative Example 1, the metal body was extracted and the wall thicknesses of the branch portions of the inner layer, the outer layer, and the central layer were measured. The results are shown in Table 1.
(2) Short-circuit failure rate With respect to the obtained batteries of Example 1 and Comparative Example 1, 100 internal resistances were measured, and the occurrence rate of short-circuit failure was examined. The results are shown in Table 1.

(3) Results From Table 1, the following is clear.

The short-circuit failure rate of Example 1 in which the wall thickness Do1 of the branch portion in the outer layer of the metal body and the wall thickness Do2 of the branch portion in the inner layer is smaller than the wall thickness Di of the branch portion in the central layer and 15 μm or less is the wall thickness. Do1 and Do2 are smaller than Comparative Example 1, which is larger than the wall thickness Di. In addition, the short-circuit failure rate of Example 1 is as low as 0%, which is extremely high quality.
As a result, in Example 1, when the electrode group was produced, the metal plate protrusion of the positive electrode plate generated by winding, that is, the broken branch portion was prevented from breaking through the separator and coming into contact with the negative electrode plate. I understand.

1 is a partially cutaway perspective view of a cylindrical non-sintered nickel metal hydride secondary battery according to an embodiment of the present invention. It is a cross-sectional view of the battery of FIG. It is a perspective view which shows the metal body used for the positive electrode plate of FIG. FIG. 4 is an enlarged view schematically showing a region IV in FIG. 3. FIG. 4 is a diagram schematically showing an enlarged region V in FIG. 3. It is a cross-sectional view which follows the VI-VI line of FIG. It is a cross-sectional view which follows the VII-VII line of FIG.

Explanation of symbols

10 Exterior can
22 Electrode group
24 Positive electrode plate
26 Negative electrode plate
28 Separator
35 metal
36 Inner layer
38 outer layer
40 Middle layer
42a, 42b Branch

Claims (1)

Cylindrical type comprising a cylindrical outer can having conductivity and an electrode group that is housed together with an alkaline electrolyte in the outer can and is formed by winding a belt-like positive electrode plate and a negative electrode plate in a spiral shape with a separator interposed therebetween. In non-sintered alkaline storage batteries,
The positive electrode plate includes a three-dimensional network metal body composed of a plurality of cylindrical branch parts and nodes where the branch parts cross each other, and an active material filled in the metal body,
The mass per unit area of the metal body is 200 g / m ² or more,
When the wall thickness of the branch portion at the central portion in the thickness direction of the metal body is Di and the wall thickness of the branch portion in the vicinity of both surfaces of the metal body is Do, Do is smaller than Di and 15 μm. A cylindrical non-sintered alkaline storage battery characterized by the following.

Images